Ultra high frequency electron discharge device



June 21, 1949. N. E. PRYsLAK Erm. 2,473,959

ULTRA HIGH FREQUENCY ELECTRON :DISCHARGEl DEVICE Filed March 28, 1947 Patented June 2l, 1949 ULTRA HIGH FREQUENCY ELECTRON DISCHARGE DEVICE Nicholas E. Pryslak, Florham Park, and Kenneth M. McLaughlin, Summit, N. J., assignors to Radio Corporation of America, a corporation of Delaware Application March 28, 1947, Serial No. 737,890

9 Claims. (Cl. 25o-27.5)

' The present invention relates to electron discharge devices and more particularly to electron discharge devices useful at ultra-high frequencies,

Y and to a method of manufacture and assembly of such devices.

The invention relates generally to electron discharge devices of the type wherein the electrodes comprise concentric tubular elements and wherein one of the electrodes is supported on a conducting plate which extends through thel walls of the device envelope and is sealed thereto, and serves as an electrode lead. The invention particularly concerns an arrangement in such device wlhrein the grid is supported on the conducting p a e.

I The practice with respect to such electron discharge devices heretofore has been to provide the grid structure with an eyelet which 1s peened to a' central aperture in the conducting plate for support thereon. The peening operation has involved the use of two tools, one to apply pressure to the eyelet from one direction to suitably deform Y it in peening and the other applied from the opposite direction to serve as a backing to absorb the pressure applied to the first tool. The use of two such tools has made accessibility to the grid and its supporting conducting plate or disc necessary simultaneously from the two opposite ends of the envelope of the device. In a structure involving this practice, the anode is supported at one end of the envelope and the cathode at the other end, the grid being mounted on the disc lead intermediate the anode and cathode.

Under the practice as heretofore followed re quiring the use of two tools for peening the grid to its support, neither the cathode nor the anode can be mounted prior to xing the grid to its sllpport. This has resulted in the necessity for a two-part structure for forming .each of the anode and cathode, one part comprising a portion of the tube envelope which is properly spaced and aligned during assembly of .the envelope parts and serving as an electrode support and the other part comprising the electrode. These support parts are provided with longitudinal passageways therethrough which have sufficiently large cross sections to accommodate the tools employed in. peening the grid to its disc support and for receiving the electrodes.

. The use of a two-part structure for the electrodes which are mounted in the two extremities of the tube is characterized by many disadvantages. For example, a two-part structure has heretofore involved a discontinuity in the outer surfaces of the electrde's'under' consideration.

-Since ultra-high frequency devices of the type referred to are designed to function in association with concentric line conductors. the ridges or depressions in the outer surface of the electrodes referred to frequently interfere with proper engagement between such surfaces and contact fingers on the concentric line. Another respect in which a two-part electrode is undesirable is the fact that such an electrode includes a substantial area between the two parts thereof which are not joined integrally but are merely in surface contact, which in some instances is incomplete. This defective surface contact affects ultra-high frequency operation in a harmful manner. For instance lt contributes to a reduction in the radio frequency power output of the tube. Furthermore, a relatively close tolerance is required between the several parte of each of the electrodes referred to, especially the anode, to reduce as much as possible the loss in radio frequency power output. Such relatively close tolerance is diihcult to achieve and represents an added cost in the manufacture of the device.

While the practice in the manufacture of an l electron discharge device of the type referred to of peening the grid to its disc support has made necessary a two-part structure for each of the anode and cathode electrodes in association with 1 their supports, this manner of mounting the grid quencies, as explained above.

on its support is also accompanied by serious ob=l jections. Thus the peened engagement between the grid and its support involves a surface Contact which sometimes is defective and thus contributes to poor operation of the device at ultra-high fre= in addition the force required in performing the peening opera= tion sometimes results in damage to the device thus further adding to the expense of manufacl ture.

It is evident from the foregoing that the practice of peening the grid of'a type of device under consideration, to its support, limits the anode and cathode to structures having the undesirable fea tures mentioned and therefore modification to avoid the peening step in the method of mounting the grid on its support is necessary before the problems presented by the structures oi the other electrodes of the tube can be suitably dealt with.

But heretofore greater dimculties have been encountered in alternative proposals for mounting the grid on its support than have been associated with the -peening method. For example, a reexcessive heat might impair the glass to metal seals of the device. The electric power required for welding would involve current conduction `through the conducting plate or disc lead on which the grid is to be mounted. Ifthis plate should be excessively heated there is the hazard that its seals to the glass envelope might be harmfully affected. And due to the relatively large surface engagement between the eyelet of the grid and the disc lead a relatively large current value would be required for effecting a welded .1olnt between these elements, and excessive heat in the disc, due to such large current value, would be difficult, if not impossible, to prevent.

Accordingly it is an object of the invention to provide an improved electron tube useful at ultra'` high frequencies.

Another object is to provide an improved elecelectrode is accomplished in a novel manner.

A further object is to provide an electron discharge device wherein no defective surface contact exists between the respective input and output electrodes thereof and their supports.

An additional object is to provide an electron discharge device which can be employed advantageously in association with a concentric line.

Another object is tov provide an electron discharge device in which the elements thereof have reduced tolerance requirements.

A still further object is to provide an electron discharge device having improved radio frequency output at ultra-high frequencies.

An additional object relates to a novel mounting of the grid on its support which avoids defective surface contact therebetween and eliminates the dependence on a two-part structure at least for one of the other electrodes for its accomplishment.

Further objects and advantages of the invention will become clear as the description continues.

While the invention is pointed out with particularity in the appended claims, it may best be i understood from'the detailed description of an embodiment thereof taken in connection with the accompanying drawing, in which:

Figure 1 shows a longitudinal section of an electron tube which includes the structure of our invention and has been made by our novel method; and

Figures 2 to 5 inclusive illustrate steps in manufacturing our novel electron tube, Figures 2 and 3 showing the step of positioning the grid on a welding electrode with its lower portion ared by being forced down on a shoulder of. the welding electrode; Figure 4 indicating in detail the engagement of the flared portionk of the grid with beveled walls of the grid support, andV Figure 5 depicting the relative position of the parts during the welding of the grid to its 4 Y Il, grid Il and cathode I ,8, are mounted in concentric relation within the envelope.

Each of these electrodes and their supports and lead-ins are of novel construction contributing to ease of manufacture of the device and to good operation thereof. The vadvantages resulting from the novel structures and organizations of our invention will become apparent from the following detailed description thereof.

The anode I4 is part oi' the integraloelongated flanged body I2, the several portions of which have different utility. The peripheral flange Il on body I2 is sealed to glass member I0 at Il. The flange I1 is positioned intermediate the ends of body I2 and closer to one end thereof than to the other. The shorter end portion I4 of body I2 extends into the envelope of the device and includes the work surface of the anode. Member I2 has a passageway I8 extending longitudinally therethrough which includes the required recess in anode I4 for receiving theggrid and cathode, and in addition aording communication between the exterior and interior vof the envelope for the purpose of evacuation. Since no tool is required to be inserted through passageway I9, it need not be wide. The exhaust tube 20 employed in such evacuation is shown pinched off to seal the passageway after completion of the device. The portion of body I2 extending outside of the envelope serves as a lead-in for the anode.

The utilization of an integral body having portions thereof serving in the several respects mentioned is accompanied by many important advantages. The device described is intended to operate at ultra-high frequencies. At these high frequencies it is desirable to use concentric transmission lines in association with'the device. Such transmission lines are usually connected to lead-ins of the device by means of ngers contacting the surface of such lead-ins. It is an aid in accomplishing the desired contact between these fingers and the lead-ins if the surface of such lead-ins is smooth. If discontinuities should be present in the lead-in surface, such as 'depressions or ridges, over which the contact the lead-in.

Inorganizations where the anode and its leadin are separate structures, such breaks in the surface are difficult to eliminate. This is for the reason that structures of the general type under consideration have heretofore included a brazed joint between the anode and its lead-in at a surface portion over which the contact fingers of the transmission line are required to pass.

Another respect in which the one-piece structure of the anode and its lead-in is advantageous is that it reduces losses in radio frequency power output. In the two-piece anode construction as heretoforeI employed, one piece comprised an outer sleeve for receiving the anode. Both parts were silver plated to provide a low resistance path to radio frequency and to facilitate sealing to glass portion of the envelope. It was necessary to ream this outer sleeve to extremely ne tolerances to receive the anode barrel in a snug fit.

surance In some instances bare steel was exposed as a result of the reaming operation, which caused a noticeable loss in radio frequency power output. The inclusion of the anode in a one-piece structure, as our invention provides, avoids this power loss and eliminates the expense of the close tolerance reaming operation.

Employment of this novel and desirable onepiece structure of the anode is possible as a consequence of a further novel feature of our invention. This feature concerns structural characteristics of the grid I and its support 2| which permit mounting the grid on its support by an operation that requires accessibility to the in-y terior of the envelope from one end thereof only. These structural characteristics are, a grid oi' cage or wire construction throughout its entirety having one end 25 thereof spread or flared outwardly, and a grid support 2l of a plate-like structure having an aperture or passageway 24 therethrough provided with beveled or frustoconical walls.

These structural characteristics of the grid and its support permit a method of mounting the A grid on its support to be used, which mechanically requires only a forced contact between the flared `portion of the grid and the beveled walls of the passageway in its support. Such forced contact between these elements can be accomplished by applying a force longitudinally of the device through one end thereof to the flared end of the grid to seat this end in contact with the beveled walls in the support. Good contact between these parts results from the application of such longitudinal force because of the translation of a part oi' such force by the beveled and flared parts referred to, into a transverse component. The sum of such longitudinal and transverse components results in a force normal to the surfaces of the beveled walls of the passageway and the flared portion of the grid. To properly allow the grid end portion 25 to contact the beveled walls of the passageway 24, the plate 2l ls mounted with the wider end of passageway 2t therein, facing the open end of the device remote from the elongated member I2.

The forced contact between the flared end 25 of the grid and the beveled walls of passageway 2t is all that is required mechanically to ilx the grid to its support but such surface contact alone is insufllcient to complete the mounting of the grid on its support and a further non-mechanical means is employed to complete the mounting of the grid.

Heretofore one method of accomplishing a complete mounting of the grid on its support has involved the provision of an eyelet at one end of the grid and a peening of this eyelet to its support through a passageway thereinv having walls normal to a surface of the support. This has required the use of two tools applied from opposite end openings in the envelope. But the contact resulting from such peening operation between the grid eyelet and the grid support was a pressure type friction contact and was objectionable in that it contributed to a loss in power output of the device.

Our invention eliminates the need for an eyelet on the grid and does not rely entirely on mechanical contact between the grid and its support. It is feasible according to our invention to provide a weld between the flared end of the grid and its support. The relatively small surface engagement between the wire strands in the flared portion of the grid and the walls of the passageway in its support. requires a welding current of less magnitude than would-be requiied for welding a grid eyelet to the grid suppor The value of the current employed inthe welding of the grid toits support is important in connection with the device of the type described. It will be noted that the grid support 2| is sealed to glass members I0, Il at 22, 23. In welding the grid to its support, electric current would be required to. transverse the supporting plate 2i including the portion thereof at which these seais are located. Too high a value of such current would heat the plate 2I to such an to impair the seals referred to. Such undesirable high value of current would be required in welding a grid eyelet to the grid support due to the relatively large surface engagement involved therebetween, but is avoided according to our invention by the limited surface contact of the parts to be welded as explained above.

The welded Joint between the grid and its support thus permitted by the novel structures of the grid and its support is advantageous from the several standpoints of providing a direct metal to metal contact between these elements, resulting in higher power output of the device, permitting a method of manufacture to be followed that requires only one open end of the device, and allowing the use of a one-piece structure for the anode and its lead as described above.

The cathode end of the device, while subject to the requirement of providing a working space therethrough for accommodating tools required for mounting the grid upon its support, includes va novel structure that not only provides this necessary communicating space, but in addition contributes to ease of manufacture of the device and good operation thereof. The end of the device which includes the cathode I6 is provided with sleeve I3 having a peripheral flange 26 at one end thereof which is sealed to the envelope glass member Il at 2l. Sleeve I3 also has an inwardly extending flange 28 which serves as an abutment for sleeve 29 disposed within sleeve i3. Sleeve 29 is provided with a shoulder 30, the surface of which is involved in the abutment referred to. Sleeve 29 is sealed to the inner wail of sleeve I3 at 3i, as by brazing. It will be noted that the sealing point is entirely within sleeve i3 and somewhat removed from the end thereof remote from the envelope. The end of the sleeve I3 remote from the envelope is suitably sealed as by a vitreous body 32. This manner of mounting the sleeve 29 within sleeve I3 does not require a vacuum type seal at 3i, since the vacuum type seal at this end of the device is made by body 32. Cathode support sleeve 33 is mounted on the end of sleeve 29 which extends into the envelope of the device. Cathode I6 is in turn mounted on support 33. The cathode I6 is indirectly heated by means of a heater wire 3d.

The advantages resulting from this structure of the cathode end of the device are important. The use of two sleeves 29, I3, permits the outer sleeve I3 to describe a relatively wide passageway to the interior of the device. This is important for permitting the entry of suitable tools into the device for mounting the grid upon its support. In addition this structure permits the outer surface of sleeve I3 to be unbroken and therefore renders it suitable for good engagement with contact flngers of an associated concentric transmission line, the advantages of such contact being more extent as 8 with reference to the grid ID and anode I4. The cathode structure is so dimensioned that when shoulder 30 on sleeve 29, engages theange 28 on sleeve I3, the cathode I8 extends toa desired operating position within the anode I4 and grid I5. With shoulder 30 in abutment with flange 28 mounting of the grid from one end only of the device. This manner of mounting the grid is in turn dependent upon an adequate communicating space to the interior of the envelope through the cathode end of the device.

i The structure of the parts-of the device forming the electrodes and their lead-ins or supports permits a novel and advantageous method to be employed in their assembly to form the completed device. This novel method is described and claimed in our co-pending application Serial No. 52,082, filed September 30,1948, and assigned to the same assignee as the present application. The envelope parts including the one-piece anode part I2, the glass members I8, II, the conducting plate 2| and the sleeve I3 are first assembled and sealed together by the use of a centering and spacing mandrel or jig, not shown. This results in a proper spacing and centering of anode I4, conducting plate 2| and sleeve I3. The glass members I0, I I are properly centered by engaging annular ridges 35 on the flanges I1, I9.

After these parts have been assembled and sealed as indicated the grid I5is fixed to ,plate 2 I.-

Before applying the grid to the plate 2I the grid is threaded on a portion 36 of a welding tool 31 having a shoulder 38, as shown in Figure 2. Grid the end of sleeve 29 remote from the cathode is brazed at 3l to sleeve I3. Thereafter a stem of insulating material 32 such as glass is sealed across the open end of sleeve I3 with the heater leads 34 passing therethrough.

The final step in the manufacture of the device is the evacuation ofthe interior of the envelope through exhaust tube 28, which is then sealed as by pinching.

The foregoing description of an embodiment of the invention is presented with a view to apprisl ing persons skilled in the art of one Way in which itmay be carried out. Of necessity much detail not required for practicing the invention has been included in this description. It is not intended,

. therefore to-limit the invention to the precise of said envelope and having smooth external sur- I5 is manually forced against shoulder 38 until y one end thereof engages the wider part of shoulder 38. This step results in the formation of a fiare 25 at this end of the grid as shown in Figure 3. With grid I5 thus engaging the portion 36 and shoulder 38 of Welding tool 31, this tool is inserted into Athe passageway 24 in plate 2I with its shoulder 38 forcing the ared end 25 of grid I5 against the beveled walls of the passageway. Suitable longitudinal pressure is applied to tool 31 to assure good contact between the flared end of the grid and the beveled walls referred to, as shown in Figure 4.

The welding tool 31 comprises one terminal of an electrical circuit which includes the ared end 2'5 of grid" I5, the conducting plate 2l, and

a cup shaped electrode 39 as shown in Figure 5.

Due to the relatively small area of surface engagement between the wires of the grid at its flared portion and the wallsof passageway 24, a welding current of a value below that which would heat plate 2I to an extent to impair seals 22, 23, is suflicient for accomplishing a weld between the flared end of the grid and the walls of the passageway.

After the weld has been accomplished the welding tool 31 is removed from the device and a `centering tool, not shown, is inserted for centering the grid I5 with respect to the anode I4. This centering tool engages the inner walls of sleeve I3,

which have previously been centered with respect to the anode.

The centering tool is then withdrawn and the cathode 'structure comprising sleeve 29, support 33, cathode I6 and heater 34, is inserted in sleeve I3. This structure is centered with respect to sleeve 29 as by a jig, not shown. Sleeve 29 engages the inner walls of sleeve I3 in a relatively tight fit and the cathode is centered by such flt faces for connection to a concentric line, one of said lead structures being integral with one of said electrodes, another of said lead structures comprising a conducting plate having an aperture therein, said aperture having beveled walls, and another of said electrodes supported in said aperture and engaging said beveled Walls.

2. An electron discharge device having an envelope, a conducting plate having an aperture and extending and sealed through the walls of said envelope, said aperture having beveled walls,

alcage type grid extending through said aperture and having one end flared, said flared end contacting said beveled walls and being welded thereto.

3. An electron discharge device having an envelope, a conducting plate extending and sealed through the walls of said envelope, said plate having a passageway therethrough, said passage- Way having frustoconical walls, whereby one end ofsaid passageway is narrower than the other, a cage type grid extending through said passageway and having one endflared, said flared end Y contacting said frustoconical walls and kbeing welded thereto, said grid extending from said narrower end of said passageway. q

4. An electron discharge device -having a tubular envelope, an electrode assembly comprising an elongated conductor having a transverse iiange intermediate its ends, said ange being sealed to and closing one end of said envelope. the inner end of said conductor serving as an electrode andthe outer end as a lead, a second electrode assembly having a ange intermediate its ends, said ange being sealed to and closing the other end of said envelope, and a third electrode assembly intermediate the two ends of said envelope including a plate extending transversely of and sealed to said envelope, and having an aperture, said elongated conductor having a recess extending from the inner end thereof, a grid within said recess and supported by said plate,

said second electrode assembly supporting a cathode within said grid.

5. An ultra high` frequency electron discharge device having an envelope and a plurality of electrode units mounted therein, one of said electrode units comprising an elongated tubular metallic member having a flange extending outwardly and radially therefrom and disposed intermediate the ends thereof and sealed to said envelope, a portion of said tubular member extending into said envelope and comprising an electrode, and another portion extending exteriorly of said electrode and comprising a lead-in for said electrode, said another portion having a continuous and smooth outer surface for effectively engaging contact members of a coaxial line, and other of said electrode units comprising tubular support having a radially and outwardly extending flange at one end thereof, said flange being sealed to said envelope with said tubular member extending exteriorly of said envelope and having a continuous and smooth outer surface for engaging other contact members of said coaxial line, and another electrode supported by said tubular support and extending into said envelope.

6. An ultra-high frequency electron discharge device having an envelope and tubular electrodes mounted with their work surfaces in concentric relation in said envelope, a, metal plate sealed coaxially and transversely of said envelope and supporting one of said electrodes, another of said electrodes constituting one end portion of said envelope and a lead-in terminal, a third of said electrodes being mounted at the other end portion of said envelope, a, support for said third of said electrodes, said support constituting a hollow tubular member having a transversely and outwardly extending flange at one end thereof, said flange being sealed to said envelope, said third of said electrodes being supported within said tubular member, said tubular member having a smooth and continuous outer surface extending externally of said envelope and constituting a lead-in terminal, whereby good line coupling to said electrodes is permitted.

7. An ultra-high frequency electron discharge device comprising a tubular envelope and tubular electrodes mounted with their work surfaces in concentric relation in said envelope, a metal plate sealed coaxially across said envelope and supporting one of said electrodes, a hollow tubular member having a flange at one end, said flange being sealed to an end of said envelope whereby said tubular member projects externally of said envelope, another of said electrodes supported within said tubular member in electrical contact therewith, said tubular member constituting a lead-in for said another of said electrodes, a third of said electrodes comprising another hollow tubular member, a flange on said last named member extending radially outwardly therefrom, said l0 flange being sealed to the other end of said envelope', a portion of said last named member extending within said envelope and comprising the work surface of said third of said electrodes, an-

other portion of said member extending exteriorly of said envelope and-constituting the leadin for said third of said electrodes, said another portion having a. smooth surface whereby good line coupling to said device and good operation thereof at ultra-high frequencies are obtained.

8. An ultra high frequency electron discharge device having an envelope and tubular electrodes mounted with their work surfaces in concentric relation within said envelope, a support for one of said electrodes, said support comprising a tubular member having an outwardly radially extending flange at one end thereof, said flange being sealed to one end of said envelope with said tubular member extending exteriorly of said envelope and having a smooth outer surface, a second support for said one of said electrodes, said support being fixed to the interior surface of said tubular member and displaced from the end thereof remote from said flange, a stem of insulating material positioned in said tubular member adjacent the end thereof remote from said flange and forming a vacuum tight seal for said envelope, said tubular member constituting a lead-in for said one of said electrodes.

9. An ultra-high frequency electron discharge device having an envelope, an elongated tubular member, an annular metallic flange on said member, said flange being sealed to said envelope, said member comprising an end portion of said envelope an electrode and a support and lead-in for said electrode, another elongated tubular member having an annular metallic flange, said flange being sealed to said envelope, said last named member comprising another end portion of said envelope and a support and lead-in for another electrode, and a platelike member sealed through the walls of said envelope comprising a support and lead-in for a third electrode and having a beveled wall passageway, said third electrode extending through said passageway.

NICHOLAS E. PRYSLAK. KENNEIH M. MCLAUGHLIN.

REFERENCES errno The following references are of record in the ille of this patent:

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